The invention is in the field of equipment and supplies for bottled oxygen users, and in particular pertains to apparatus for use to assist out-patient who use oxygen on a semi-regular, or regular basis.
There are many people suffering from emphysema and other pulmonary and cardiovascular diseases who must supplement the earth's oxygen with a supply of concentrated, bottled oxygen. This supply is ordinarily delivered to the patient through a narrow, flexible plastic tube which forks near the end to provide two tubes, encircling the head or neck from both directions to meet at a central cannula comprising a pair of parallel, short spaced tubes which are inserted into the nostrils of the patient. The patients breathes in and out normally and thus receives an extra dose of oxygen with every breath.
The amount of oxygen the patient should have supplemental to the earth's oxygen is ordinarily prescribed by the physician, and is prescribed in terms of the number of liters per minute of oxygen flow that the patient requires. Thus, a patient typically might require one liter per minute, two liters per minute, or even three or four.
The oxygen tank which the patient uses has a volumetric flow regulator which ensures that irrespective of the pressure required to deliver, the volumetric flow will be maintained at the pre-set level. Typically, the oxygen supply line passes through a humidifier bottle, which essentially bubbles oxygen up through water in a cannister. The cannister is provided with an escape valve in case the line is kinked or snarled downstream from the cannister so that the cannister will not explode as the volumetric flow regulator on the bottle continues to force oxygen into the bottle at the rate of the prescribed number of liters per minute despite the fact that the blockage has occured.
For this reason, kinks and obstructions in the line downstream of the humidifier will result in the dissipation of the prescribed oxygen to the atmosphere, without delivering it to the patient. Because some patients may have lines that are fifty feet or more long for convenience in moving about a house or apartment, it is not uncommon for the lines to get kinked. Because of the escape valve in the humidifier, the kinking may not become apparent, and many perhaps even the majority, of the oxygen users cannot feel whether or not the oxygen is being delivered through the nasal cannula. Therefore, very often the patient may not be getting the oxygen that the doctor has prescribed, or the amount that the patient thinks he is getting by the reading on the oxygen bottle.
A similar result occurs when the humidifier cannister is refilled, but the bowl is not screwed tightly enough into its gasket to prevent the escape of oxygen at pressures well below the escape valve pressure of the cannister. And, there are other ways in which the oxygen will register a certain flow rate in liters per minute at the oxygen bottle and yet not be delivered, or not be delivered in full, to the cannula. When the patient is unaware of this and cannot correct the situation, obviously the problem for which the oxygen was prescribed as a remedy will not be resolved, and the patient may suffer organ damage, unconsciousness, and in an extreme case even death.
It is not practical to measure the volumetric flow at a junction between lengths of tubing, because the connectors are so tight that even a strong, heathly person sometimes has trouble separating the tubes at a junction. There is a need, therefore, for a volumetric flow meter that can be used right at the cannula, right at the point of delivery of the oxygen to the patient so that there is no possibility of any intervening blockages between the flow meter and the oxygen.